Pulse propagation in arteries will be investigated both experimentally and theoretically. The predictons of a new nonlinear theory, which can determine the complete flow field along an artery from two pressure measurements, will be compared with the in vivo measurements carried in major arteries of dogs. Effects of geometric and elastic tapers, nonlinear elastic response of the arterial walls will be studied. Flow in a bifurcation will be investigated in vivo. The geometry of the junction and the pressure-area variation will be studied, and pressure gradients and velocity profiles will be measured along the main artery and its branches. Also behavior of the flow through rigid and distensible models of a bifurcation will be studied and compared. Using a recently developed technique which enables one to measure velocity profiles of a streaming liquid in the immediate neighborhood of a vessel wall (within a distance of 200 microns), the slip phenomena will be investigated.